How to make blend file take up less space
A few things come to mind. These affect not only filesize, but also performance.


Keep modifiers procedural as long as you can (Subdivision Surface, Array, Mirror, etc. Basically any modifier that adds geometry.)
Use linked duplicates, instancing and collection instances whenever you can. Instances don't increase filesize and are also better performance wise.


Procedural Modifiers - filesize 650KB



Applied Modifiers - filesize 20MB (30x increase)